Garage floor slab not in water - sanding

Does the slope fall in the wrong direction? Or across the goal?

Thank you very much for addressing my problem. I have the height difference not in the depth but in the width. Thus, the gate (not yet ordered) would already reach the ground on one side, while on the opposite side 4 cm are still missing.

Hello,

it's hardly a problem for the gate manufacturer, as long as he knows about it before the order. The floor sections can also be custom-made with the corresponding slope. Yes, it costs a few euros more than the normal section, but grinding the floor slab is really not an option. Your floor slab has at least 30mm of concrete cover up to the top reinforcement; if you happily grind down 40mm, the steel will be exposed. Cracks, rusting surface, structural integrity... Right?

I estimate that the modified floor section will not cause more than 100€ in additional costs.

The roofer probably ran out of about 1m3 of concrete in the end, there's no other explanation. You could grind the concrete and create a proper primer with concrete contact or 2k epoxy resin and level it with industrial floor self-leveling compound. ( but it's expensive, 60-70€/m2 just material) or fill it up with cement screed. I would adjust the gate if money is an issue.